Pole-mounted pruning tools are widely used by those involved in caring for tall trees and plants. To control foliage growth at substantial heights, pruning tools are commonly used by arborists and others involved in landscaping. Conventional tree pruners usually comprise a pruning head mounted atop a pole with the lower section of the pruning head connected to the upper end of the pole. The upper section of the head typically supports the cutting implement which is normally operated by a pull cord or other leverage member extending to the lower end of the pole where it can be easily engaged by the operator.
Such pole-mounted cutting implements usually comprise a jaw having a cutting edge cooperating with a moving blade. As shown in prior art patents such as U.S. Pat. No. 4,760,645 to Davis, these cutting mechanisms typically consists of two pieces of metal passing over each other in a scissorlike action. However, since scissors operate on the principle of shearing to cut material located between the two blades, scissors are more adapted to cut thin material than they are to trim tree branches. This is because, as a cut is being formed in the tree branch held between the two blades, friction results from the pinching of part of the branch held by the blades, thereby reducing the efficiency of the cutting tool.
Pinching and friction problems have already been recognized and addressed by those skilled in the tree trimming art. U.S. Pat. No. 4,096,630 to Honick discloses a pole pruner apparatus designed to provide a solution to the some of these problems. In such a device, the cutting mechanism comprises a cutting blade and an anvil coupled to substantially parallel respective stems. During the trimming operation, the branch to be trimmed is held by the anvil advancing toward the downward moving cutting blade. The cutting force applied by the operator to a pull cord is transmitted through a series of levers to the two stems moving in opposite directions following a linear path. Devices of the type described in the Honick patent, however, necessitate a significant number of parts to translate vertical action on the pull cord into oppositely moving blade and anvil.
Single blade, pass-through cutting implements have also been devised as another way to avoid pinching and friction problems during tree trimming operations. Photographs of the Corona model 1510 tree pruner illustrate an example of a pruning tool using this approach. In such a pole-mounted tool, the cutting blade passes through the area where the branch to be trimmed is disposed. With this tool, as with the blade-anvil device, no pinching of part of the branch being cut occurs. It should be noted, however, that pass-through tree pruners have the advantage over anvil-type tools of requiring fewer parts of lenient tolerances.
Tree pruners also normally include biasing means by which the cutting blade is maintained in an open position, allowing the tree pruner to engage the branch or limb to be trimmed and returning the movable blade to its open position after the trimming operation has been completed. The most commonly used blade return mechanism usually comprises an exposed tension spring linking the cutting blade or blade-actuating lever to the pruning head as shown in the Honick patent and Corona device.
In normal use, tree pruners are usually guided by the operator through areas heavily congested by branches of trees or plants to reach the limb to be trimmed. Accordingly, while tree pruners of the type described above have been used for a great number of years, and while non-scissorlike pole mounted tree pruners are desirable to alleviate the problems associated with various scissor-like pruners, the present inventors have specifically addressed solutions of the problem that the typically exposed return mechanisms of prior art tree pruners usually get caught in the branches of the plants or trees as the operator guides the tool through these branches.
Thus, it is desirable to have a tree pruning tool which can alleviate the problems associated with scissor-like devices and in which the blade return mechanism is disposed so that the tree pruner is less susceptible to getting caught in congested foliage areas, without undesirably affecting the performance of the tool.